Drill bit



Feb. 25, 1936. M, E REEDY A 2,032,328

DRILL BIT Filed Deo. 19, 1935 2 sheets-sheet 1 T Il" f :IE- l Il,

3k Ira- E ,9 y,

| /j r/ {'I l J I I 5 f, INVENTOR.

y i @VCM/wlw 6. @lez/15% 2? BY FM JDM, 2,5 43 47 4.5' ATTORNEYS.

v Feb. 25, 1936.

y M. E. REEDY DRILL BI'1 Filed Dec. 19, 1953 2 Sheefs-Sheet 2 'iIr-:TQLE l INVENTOR l am ATTORNEYS.

Patented Feb. 25, 1936 UNITED STATES PATENT oFFlcE I 2,032,228 mum. Brr

Melvin E. needy, ATulsa, om, signor a Franklin G. Reedy, Warren, Ind.

Application December 19, 1933, semi No. 703,110

' 13 claims. (cl. 255-63) cable drilling, and it is particularly withrefer-` ence to the latter method that the present invention isdirected. In this method' of drilling, a relatively heavy drill bit issuspended at the end ofa longcable which is raised and lowered by meansof a walking beam, jerk line, or other means of imparting thereciprocating drilling motion to the cable 1.; and tools. The drill bit,always the lowermost member of the assembly ofthe various drillingtools, is usually of very substantialweight and includes a cuttingsurface at the lower end, a body of five to eight feet or more inlength, and

a wrench square above which is a threaded tapered pin which is attachedto the threaded tapered box at the lower end of the drilling stem. 'Iheupper or opposite end of the drilling stem has a threaded tapered pin towhich is attached the threaded tapered boxof the rope socket attached tothe lower end of the drilling cable, or a set of Jars may be interposed.When such drilling tools, whose suspended assemblies weigh severalthousand pounds in the larger sizes of hole, strike thc bottom of thehole, they. exert a tremendous force and particularly when in contactwith the harder viormations are subjected to great shocks, and excessivevibration. f

In the drill bits proposed by' the prior art, it

has been' customary to employ bits which are provided. 'withfrelatively'flat chisel-like cutting surfaces, and therefore likely to have theirvertical direction altered'in contacting certain diflicult formations.in the earth. To prevent this deflection, various proposals have beenmade' for changing the character of the bit cutting surface,

orfor adding reaming members to thefbit body,

55 removal is diillcult, if not practically impossible.

It is therefore among the objects of the present invention to provide adrill bit preferably made as a single unitary structure which isvattached to the drill stem by the usual threaded tapered pin and boxjoint, and provided with 'a pilot point. 5 that dlrects'the drill bit atthe bottom of the hole and makes a straight hole.

It is also an object to provide a drill bit which has a tapered end sothat the cutting end of the bit does not contact a flat bottom in thehole, but 10 produces a hole with a concave bottom, with weakened edgeswhich are readily broken away and mixed with the drilling fluid.

It is a further object to provide a novel method. of preparing drillbits embodyingytherpresent in- 1 5 vention and also a method by means ofwhich the conventional drill bit's now in service may be adapted to theform proposed in the present invention in a simple and expedient manner.

It is a further object to prepare a drill bit, Prov20 vided with a pilotpoint and a tapered end upon which stepk cutters are formed, which makesa concave bottom with weakened sides, thereby greatly reducing the shockand vibration on the pins and boxes and other sections of the drill- 25ing assembly and minimizing breakage of samc.

It isa still further object to prepare a drill bit provided with a pilotpoint and a tapered end upon which step cutters may readily be formedand surfaced with a hard, wear resisting alloy, 30 giving long rlife tothe bit `and making for more rapid drilling progress.

Further objects include the provision of auxiliary peripheral reamingcutters which maintain the gauge vthroughout long service and prevent 35tapering of the hole being drilled.

These and other objects which will be apparentl from the sequentdescription are all embraced within the present invention, illustratedin the 40 accompanying drawings, in which;

Figure 1 is a front'elevation Aof a drill bit embodying one modificationoi' the present invention;

Figures 2 andl 3 are side and bottom views, 45 respectively, of the sameembodiment, showing only the cutting end;

Figures 4, 5, and -6 are front, side and bottom views, respectively, ofthe cutting end oi' a second modification; v

Figures 7 and 8 illustrate the' steps in preparl ing a drill bitembodying the present invention from a conventional form;

, Figures 9, 10, 11, and 12 illustrate the steps in'prparing a drill bitembodying the present invention from a modified conventional form; and

Figures 13 and 14 are cross sections taken along the lines I3-I3 andI4-I4, respectively, of Fig. 3 to illustrate the method of building upthe stepcutters, anges and cutting edges as wel as surfacing them.

'I'he drill bit of the present invention, which is designed primarilyfor percussion drilling, may, of course, be embodied in other'forms forsimilar or analogous drilling operations. It involves the usu'al bitbody which is of substantial length, from five to eight feet or more.and generally cylindrical in shape, the diameter of the cylinder beingslightly less than the gauge of the hole to be drilled. To providepassages for lthe drilling fluid, portions of the cylindrical body l maybe cut away as by the intersection of chords on the circular perimeteror, in addition, by U- shaped grooves on the-flattened surfaces. Al-

ternatively, V-shaped grooves may be made into face so that the bottomof the hole is not flat but concave or, more accurately, in the'generalshape of an inverted cone. This portion of the drill bit mayassume othergenerally conical surfaces such as shapes Awhich provide a surface thatdecreases in size toward the end. At the apex of the conically taperedsurface is a gcnerally cylindrical extension which projectsl from theapex. This cylindrical extension forms a hole of substantially less sizethan that of the main portion of the hole and acts as a pilot point indirecting the drill bit. At the periphery of the conical surface, thatis', its junction with the cylindrical surface of the drill body, aflare is built up which has a diameter or gauge substantially that ofthe finished hole. On this are are auxiliary reaming cutters and inaddition one of the step cutters, more particularly hereinafterdescribed, may be included. These auxiliary reaming cuttersand the edgestep cutters maintain the proper gauge for the hole. .On

the conically tapered surface are built up what may be termed stepcutters which may be arranged in any suitable fashion, that is. eitherin direct line, helically or other more or less uniform arrangement.These step cutters are triangular in cross section, having thehypotenuse on the conically tapered surface and a right angle oppositethehypotenuse and provide a cutting surface in the general shape of anannular sector, although the non-circular edges may be those of chordsrather than radii. The side edges of the steps form substantially rightangles with the cutting surfaces and provide a sharp edge to assist inthe cutting' operation. The step cu'tters need not be, and preferablyare not, on alllv radii of the conical surface to permit the readypassage of drilling uid and since in operation the drilling toolssuspended on a long twisted cable tend to rotate and different sectorsof the conically tapered surface is also flattened on one or vtwo sidesas by chords of the circle and the bottom surface is provided with ahard, abrasionresisting metal. The -cylindrical portion of the 'acsasasextension is flared out by building up the metal so that the cuttingsurface is slightly larger on the arcuate edges than the cylindricalextension itself.

Considering now the invention as illustrated in the drawings which,however, are not to be taken as limiting, butsimply as illustrating someof the many possible modifications of the present invention, attentionis directedto Figures 1, 2, and 3, in which I is the body of aconventional drill bit that is flattened on two sides as by chords l sothat the body does not completely ll the hole. 'I'he upper end of thebit body is tapered 01T at 5, on which section is a wrench square 1.Above this is the threaded tapered pin 9 which is attached to the.threaded tapered box of the stem by wrenches used on either a. circularor straight jacking track. Extending along the cylindrical portion ofthe body of the bit on the flattened sides are U-shaped grooves I I toprovide channels through which the drilling fluid may readily now. Atthe upper extremity of the channel it may diminish somewhat to a smallerchannel II.

At the base of the cylindrical portion of the body I is a flare I1 ofslightly greater diameter than that of the cylindrical body by about .05to .10 which is substantially the gaugey of the hole. 'I'he method andmaterials used in forming this flare will be considered morespecincailyin connection with Figs. 13 and 14. Below this nare the drill bodytapers rapidly in the f orm of a conically tapered surface I9. On thisconically tapered surface are the step cutters 2| which, as illustratedin Figs. 1, 2, and 3, are diametrically opposed. Extending from the apexof the conlcally tapered surface is the generally cylindrical extension23 which serves as a pilot point. This extension has flattened sides 25.On the arcuate portions of the generally cylindrical extension a flare21 is provided and the bottom surface'is given a at, chisel-like face 2lbuilt up of wear-resisting alloy. The last step cutter from the apex ofthe conical surface, designated as 3|, is partlybuilt up directly on theare I1. Adjacent the step cutter 3| are. auxiliary reaming cutters 33which assist in maintaining the proper gauge of the hole.

As stated above, the drill bit of the present invention may either beoriginally constructed according to the teachings of the presentinvention or the conventional types of drill bits may be modified toembody the novel features herein described.

If the operator is of a drill bit gen-- .erally similar to that shown inFig. 1, except that the end has the conventional fiat chisel-likecutting surface 1 I, as shown in Fig. 7, which type of drill bit isnormally dressed by forging, he may secure the advantages of theinvention by removing the tempering and -machining' or otherwise workingthe end ofthe drill bit to secure the structure of Fig. 8 whichincludes-the bit body I with an annular cut-out portion lI, conicallytapering surface I and a generally cylindrical extension 2l from theapex of the conical surface.

Whether the structure illustrated in Fig. 8 is secured from machining aconventional drill bit or prepared in original manufacture, the stepcutters, auxiliary reaming cutters and pilot point may .ie-built up andarranged thereon in-the manner shown in Figs. 13 and 14 by electric arcor Oxy-acetylene welding.Before vbuilding up these members on the parentmetal by oxyacetylene welding -the end of the bit should be llame is notso rapidly dissipated as it is in cold metal. A tough,abrasion-resisting alloy (such as Stoody Self-Hardening," Hascrome, orother similar alloy) is welded onto the end and cylindrical side nearthe end of the cylindrical extension 23 as 'at 35 and on the conicallytapered surface |9 to build up the step cutters 2|. This alloy is alsoemployed to flare the cylindricall portion of the -bit body and form thelast step cutter 3| which is lower than the annular groove 8|.' On thesurface of the alloy used to build up these members is.welded a stillharder, wear and abrasion-resisting alloy (Stoodite, "Stellite, or otheralloys having similar properties), at 3l. This relatively thin coatingis applied on the cutting surface and the edges as well as extended ashort distance along the side.

Fig. 14 illustrates the structure of the auxiliary reaming cutters whichare arranged on the annular groove 8| and the built up flare |1. Theseauxiliary reaming cutters are built up in the same manner as the stepcutters or the pilot point and, in addition, since being on theperiphery, they are subject to particularly hard wear, they are given anoverlay of very hard alloy (such as Borium,.Haystellite Composition, orsimilaralloys). While'speciilc alloys have been mentioned in connectionwith building up the cutting elements of the bit on the parent metal, itis to be understood that these are given as illustra- .tive of thosewhich have been found successful,

i but that other alloys possessing generally simi- ,l lar propertiesmight be employed in their place.

When the cutting members, cutting edges and surfaces have been built upas described, the bit, preferably is again placed in the furnace andbrought to a Inormalizing heat, after which it is allowed to cool in theatmosphere. The step and reaming cutters on the outer circumference, i.e., 3| and 35 of the cutter head, should be kept as large or full to thegauge of the casing in the well as possible, otherwise no great careneed be taken in finishing the step cutters to any particular gauge, asin actual use a percussion method bit drills a hole having a diameter of1.05 to 1.10 or more of the greatest diameter of the bit.l

It is probable that the drill bit of the present invention may beprepared by those skilled in the art by methods other than the novelways described, but it should be understood that this invention includesthe novel drill bits by whatever method they may be prepared.

After the drill bit has been in use for some time it will, of course,wear down and thel edges of the step cutters may be rounded off to someextent and also the auxiliary reaming cutters as well as the last stepcutters may be worn down so as to decrease the diameter of the holedrilled, 4

ing up layer of alloy .and an additional layer of a harder, abrasion andwear-resisting alloy.

Figs. 4, 5, and 6 illustrate an additional modification in. which thestep cutters instead of being on a single diameter as in Figs. 1, 2-,and 3,v

are staggered or arranged helically with opposite helix on oppositesides so that each` step cutter in a given position has a correspondingstep cutter diametrically opposed as, for example, lul-4|, 43-43, 45-45,41-41. In this modication auxiliary reaming cutters 33 are also providedon the circumference. The pilot point 23 is illustrated as having theaxis of its flat, chisellike face somewhat oblique to the chords cuttingthe cylindrical surface of the bit body In Figs. 9 to 12 are illustratedthe development of abit embodying the features of the present inventionfrom the conventional cross or star 'shaped bit, which development issimilar to that shown in Figs. 'l and 8. When, however, the step cuttersof the present invention are employed in connection with a star or crossshaped bit, they are put on two axes at right angles to each other.Otherwise the arrangement is generally similar to that of theembodiments formerly considered, with the exception that on one axisthere would normally be two more cutters, as 9|, since these cutters areomitted from the conically tapered surface l93 in order that there willbe no continuous member above the cylindrical extension 23 which wouldtend to obstruct the drilling fluid and prevent its free passage alongthe sides of the bit or through the channels otherwise provided.

While the invention has been described in great detail with respect tothe several modifications thereof, these are not to be construed as -Yery of -the drill.

2. A .unitary percussion drill for earth boring having a body memberterminating at its lower end in a downwardlytapering conical surfacefrom which projects a centrally arranged cutting 'and pilot point of a.vdiameter substantially smaller than the diameter of the drill body, anda plurality of arcuate cutters on a portion of said conical surface justabove the pilot point extending in stepped relationship toward theperiphery of the drill, the several stepped cutters being formed inrelatively small segments; with intervening spaces, such spacesproviding for the 'ready 110W 0f the drilling fluid.

3. A unitary drill bit for percussion earth boring comprising a drillbody, a conically tapered end surface, arcuate cutting edges on a rtionof the conically tapered surface, a pilot int projecting from the apexof the conical surface and a channel. extending along the drill bodycutting away a portion of the conical surface. 4. A unitary drill bitfor percussion earth bor- -ing comprising a drill body, a conicallytapered end surface, permanent arcuate projections from a portion ofsaid conical surface provided with cutting edges and surfaces and 'apilot point pro- `face, arcuate projections triangular in radial crosssection permanently attached to and projecting from a portion of theconical surface in stepped relation to act as cutters.

6. A drill bit for percussion earth boring comprising a drill body, aconically tapered end .surface, arcuate projections triangular in radialcross section permanently attached to and projecting from a portion ofthe conical surface in helical stepped relation to act as cutters 7. Adrill bit for percussion earth boring comprising a drill body, aconically tapered end surface, stepped arcuate projections triangular inradial cr'oss section permanently attached to and projecting from aportion of the conical surface to act as cutters and a pilot pointextending from the Vapex of the conical surface to center and direct thedrill.

8. A drill bit'for percussion earth boring comprising a drill body, aconically tapered end surface, stepped arcuate projections triangular inradial cross section permanently attacher to and projecting from aportion of the conical surface to act as cutters, a pilot pointextending from the apex of the conical surface to center and direct thedrill and a channel extending along the drill body cutting away aportion of the conical surface.

9. A unitary drill bit for percussion earth boring comprising a drillbody, a conically tapered end surface, projections from a portion ofsaid conical surface providing arcuate cutting surfaces and auxiliaryreaming cutters on the periphery of the conical surface which extendslightly beyond the generally cylindrical surfaceV face which extendslightly beyond the said cylindrical surface ofthe drill body, a pilotpoint extending from the apex of the corneal surface to center anddirect the drill and a channel to permit the passage of drilling uidextending `along the drill body cutting away a portion of the conicalsurface.

l1. A drill bit for percussion earth boring comprising a drill bit bodyhaving a peripheral are to form auxiliary reaming andl crushingsurfaces, a conically tapered end surface, annular sectors formingcutting members including projections substantially right triangles inradial cross section disposed Ain regular stepped relation on portionsof the conically tapered surface, each projectionA having its hypotenuseon the conically tapered end surface to provide cutting and crushingsurfaces disposed at right angles to the axis of the bit, and a pilotbit with cutting edges and crushing surfaces extending' from the apex ofthe conically tapered surface.

l2. A drill bit for percussion earth boring comprising a drill bit bodyhaving a peripheral flare to form auxiliary reaming and crushingsurfaces, a conically tapered end surface, annular sectors formingcutting members including projections substantially right triangles inradial cross section disposed in helical stepped relation on portions ofthe conically tapered surface, each projection having its hypotenuse onthe conically `tapered end surface to provide cutting and crush-l ingsurfaces disposed at right angles to the axis of the bit, and a pilotbit with cutting edges and crushing surfaces extending from the apex ofthe conically tapered surface.

13. A unitary percussion drill for earth boring having a body memberterminating at its lower endin a downwardly tapering conical surfacefrom which projects a centrally arranged cutting and pilot point of a'diameter substantially smaller than the diameter of the drill body, anda plurality of arcuate cutters on a portion of said conical surface justabove the pilot point extending in stepped relationship toward theperiphery of the drill with adjacent conical surface, whereby saidarcuate cutters act tochlp oil.' earth formations at the conical bottomof the hole and the conical surface adjacent the cutters assistsl linmixing the loosened formations with the drill-l ing uid.

' MELYIN E. REEDY.

